docs: def _Aterm(N, h, m, k, dW):
      """kth term in the sum of Wiktorsson2001 equation (2.2)"""
      sqrt2h = np.sqrt(2.0/h)
      Xk = np.random.normal(0.0, 1.0, (N, m, 1))
      Yk = np.random.normal(0.0, 1.0, (N, m, 1))
      term1 = _dot(Xk, _t(Yk + sqrt2h*dW))
      term2 = _dot(Yk + sqrt2h*dW, _t(Xk))
      return (term1 - term2)/k